A 5.9 magnitude earthquake struck off the Humboldt coast Thursday afternoon, about a month after a major shaker rocked the quake-prone region.

The U.S. Geological Survey said the temblor — originally reported at magnitude 6.0 — occurred at 12:20 p.m., about 47 miles west southwest of Eureka.

Items fell from walls and shelves, but there were no reports of major damage.

Officials say the quake was not strong enough to trigger a tsunami.

Humboldt County spokesman Phil Smith-Hanes says he felt a rolling sensation, but the movement didn’t feel as severe as the magnitude 6.5 quake that struck off the coast last month about 18 miles away.

The larger temblor Jan. 9 caused more than $40 million in damage and one serious injury — an elderly woman who fell and broke her hip.

Thursday’s quake was felt as far south as San Francisco, east to Redding and north to Grants Pass, Ore.

Steve Walter, a seismologist at the USGS office in Menlo Park, said Thursday’s quake was not an aftershock because it occurred on a different fault, but “we could speculate it might have been triggered by the one last month.”

This is the seismic capital of the state, one of the few places in the world where three gigantic tectonic plates merge.

Because of the different directions and various rates of movement of the plates, the area absorbs great geologic strain and often fractures.

Research shows that every 300 to 400 years, the region experiences a quake of about magnitude 9.

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